Electronic typewriters commonly now have keyboard controlled line feed and half index up and half index down capability. Several such typewriters have micro index up and down, also. These controls allow the typist to move the paper or record sheet up or down with respect to the print mechanism, with varying increments of distance and to align the typed text to a form or to provide other non-standard index increments between the lines of text.
Clearly, this provides the typist with greatly increased flexibility and control over typewriters without such capabilities.
Unfortunately, when dealing in increments as small as 1/48th of an inch (0.529 mm), or about 1/8th of the height of the typical typed uppercase letter, the realignment of the print point at a desired point on the page or record sheet becomes difficult and the operator must guess how many such small increments are to be inserted. Parallax complicates this problem, due to different eye level positions of different operators. Without accurate realignment, it is very difficult to correct errors and position inconspicuous insertions.
Most electronic typewriters available in the market at this time reflect no attempt to address the need to accurately and automatically position the print point over a previously typed line, except to provide a reverse index feature which only reverse feeds the record sheet by the selected line feed increment, or by a fixed amount, such as a single line feed, half line feed, or micro index. Clearly if the line position is other than on a standard line feed increment or multiple thereof from the line to be aligned, the print point will not be properly positioned.
At least one commercially available electronic typewriter has the capability of storing the selected line feed, (single, double or triple space) and then when a "previous line" command is keyed, the platen drive reverse feeds the record sheet by the selected amount. The typewriter will not accommodate any deviation of the position of the print mechanism from the regularly spaced lines, and if a partial line adjustment had been made to the print mechanism position, the partial line adjustment is perpetuated in any effort to realign with a previous line. The typewriter does not have the capability of finding a subsequent or following line, and does not determine the position of a line of text in order to align the print mechanism therewith.
It is therefore an advantage of this invention that the print point of the typewriter can be positioned over one of the adjacent print lines having text, in response to a keyboard command.
Another advantage of this invention is the elimination of errors associated with attempting to position the print point of a typewriter over the text in a previously typed line of text, resulting from the misjudgment as to the print point position and from the line of text being displaced by a distance other than a standard line feed increment.